In many construction, installation, and fabrication and industrial tasks a hole needs to be made in a ceiling, wall, flooring, or panel, for passage of wiring, piping, or ducting, for installing a fixture, or other purpose. The larger the hole the less likely that a fixed size hole saw exists in the size needed, and the cost for individual custom made hole saws can be prohibitive. At the same time there are materials which include ceramic tiles and sheet metal that cannot be readily cut with the prior art designs of adjustable hole cutters.
With a material such as thin sheet metal the point of the prior art cutting blade will puncture the metal at one point in the circumference of the hole being cut and then the drill will not have sufficient power to continue the cutting operation. With ceramic materials such as with floor tile the contact area of the blade tip or edge is too small for effective cutting regardless of the blade material composition or design. A long blade edge with high speed steel or tungsten carbide teeth, or a tungsten carbide or diamond grit edge, is needed to efficiently and reliably cut these types of materials. The present invention provides an apparatus that employs long rectangular blade sections and with the ability to cut a wide range of hole diameters in these and other materials, and to provide for very small incremental changes in the diameter of the hole being cut.
Another shortcoming of current designs is the use of one or two blades for the cutting. These designs are very difficult and potentially hazardous to use without an exterior ball bearing mounted shield to support the hole cutter and keep it perpendicular to the work surface unless it is used in a stationary pillar type electric drill press. The shield adds expense and requires more working space than an adjustable hole cutter without the shield. This particular shortcomings can be overcome with an adjustable hole cutter design that provides for the use of three or more evenly spaced blades.
Increasingly there are government safety and environmental and health regulations that require dust containment while cutting with a power tool. The new hole cutter design is one that can be used with current dust shield designs and with current vacuum systems. The present invention maximizes the cutting depth for the hole cutter while enabling the hole cutting apparatus to be used with a dust shield. The apparatus also enables the user to quickly remove the shield and cut without it or to store the hole cutter and the shaft and the shield in a more compact manner for safe storage and for transport in a case.
When using a longer blade section with an adjustable hole cutter there arises a problem with the need to have a different arc of the blade or for different diameter holes. The longer the blade segment used, or the smaller the diameter of the hole being cut, or the more difficult the material is to cut, as with thin sheet metal, the greater the need to have the arc of the blade match the arc of the circumference of the hole to be cut.
An adjustable hole cutter using long cutting segments (blades) needs to provide a mechanism that is able to position the blade or blades the correct distance from the center of the hole cutter and its drive shaft or arbor, and equally important the adjustable hole cutter must also provide a means for users to adjust the arc of the blade or blades to match the arc of the hole to be cut as well. Additionally with more than one blade there is a need to provide a means to insure that the cutting blades are equidistant from the center of the drive shaft or arbor so that all blades track in the same groove. If they are not equidistant they will cut their own groove and the amount of torque and power needed from the power drill will increase proportionate to the number of blades used and the maximum hole size which can be cut with a hand held power drill will be greatly reduced.